Hi, often negative regulators perform less well.
The link shows that both PNP and NPN active devices at work, so it may be that a negative version will work just as well.

Back to your question:- the negative can be an inverted positive by swapping around the polarity of the components.
or
Build two positive regs. Connect one +ve output to the ground of the other. Call this connection your 0v common. The other two outputs are your +ve & -ve supplies.

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regards Andrew T.
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